Over the past few decades, powerful economic, political and cultural forces have restructured the welfare state and social work practice. In response, there have been calls in recent years for the re-politicisation of the social work profession. One of the main ways in which social work has been re-politicised is through the emphasis on social workers’ involvement in the policy arena, commonly referred to as ‘policy prac-tice’ in the literature. Although policy practice has recently received close attention in social work debates, it has remained relatively under-theorised. This article introduces social work scholars and practitioners to the theoretical work on policy change and elaborates its implications for how social workers can influence policy. Drawing on diverse literatures from the fields of political science and sociology, the article circum-scribes to four influential theories of policy change that provide support for informed action in the policy arena: neo-institutional theory, elite theory, resource mobilisation theory and interdependent power theory. Drawing on these theories, the article develops a conceptualisation of four different types of policy practice: institutional policy practice, elite policy practice, resource-based policy practice and radical policy practice.